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awk windows download
Download Zip: https://9haetatranha.blogspot.com/?download=2vzmhG
Basically, I need to strip the process ID from netstat so I can use it down the line in different parts of a script but have no knowledge of a native command that could do the equivalent of awk ' print $4 '. Are there any options for me? Obviously I'm quite new to windows cli.
OP: There are several windows ports of the standard *NIX tools. Try UnxUtils Download UnxUtils software for free at SourceForge.net which is freely available and includes Microsoft C-Library native versions of sed, gawk etc. they can be used directly from CMD.EXE.
DMDX is software for Windows 95+ that can be used for running psycholinguisticexperiments. It was developed by Jonathanand Ken Forster at the University of Arizona. and can be downloadedfrom here.
I borrowed very heavily from this in setting up my own DMDX tutorial whichyou can now view on-line. You can also downloadthe original presentation for usewith Microsoft Powerpoint and the filesto run the example experiments. This was written for the group at the Centre for Speech and Language so isheavily biased towards the standard Psycholinguistic experiments that were runat CSL.
NEW: I'm told that many people have had trouble downloading andinstalling this programme. I would encourage people to try to follow the stepsdescribed below and email me with any problems that they are having. I amconfident that this script will work on most Windows XP systems or earlier. Ifyou're using Vista, then all bets are off! I'mtold that paths that contain a full stop or period "." causeproblems. I would suggest that you use Jonathan Forster's AZK2COLUMNSutility instead.
1) Right click to download the zip file.Unzip this using WinZip or the standard software built into Windows XP. Youwill need to save the two files (getdat.awk and gawk.exe) on your local drive in c:\bin. (NBIt's helpful to use exactly this path - filenames with spaces can sometimescause problems). This download includes a version of awk for Windows called gawk.exe which is distributed under the GNU publiclicense as part of the djgppproject.
If you're having problems getting gawk to work from this download, Iwould recommend that you try this zip fileinstead. For some reason there is a problem downloading executables from ourwww server.
Download our AWK cheat sheetsWindows users: You can download our AWK cheat sheets as a Microsoft Word document and Adobe PDF file, zipped with WinZip for Windows, by following this link to the WinZip file. You will need an unzip utility such as WinZip or PKZIP to expand the zipped file.
UNIX users: If you are working from a UNIX machine, please follow this link to the gzip compressed Adobe Acrobat file or this link to the gzip compressed rich text file. If you are using a UNIX machine, you will need to use gzip or gunzip to decompress the files. You will also need Microsoft Word, Adobe Acrobat Reader, or another application capable of reading rich text files to view each document. You can download the free Adobe Acrobat Reader here.
eBird is an online tool for recording bird observations. Since its inception, nearly 500 million records of bird sightings (i.e. combinations of location, date, time, and bird species) have been collected, making eBird one of the largest citizen science projects in history and an extremely valuable resource for bird research and conservation. The full eBird database is packaged as a text file and available for download as the eBird Basic Dataset (EBD). Due to the large size of this dataset, it must be filtered to a smaller subset of desired observations before reading into R. This filtering is most efficiently done using AWK, a Unix utility and programming language for processing column formatted text data. This package acts as a front end for AWK, allowing users to filter eBird data before import into R.
Table of ContentsLast modified: Fri Nov 27 09:56:48 2020Part of the Unix tutorials And then there's My blogYou can buy me a coffee, pleaseI would appreciate it if you occasionally buy me a coffee. Thanks.Click on a topic in this table to jump there. Click on the topic title to come back to the Table Of Contents.Why learn AWK?Basic StructureExecuting an AWK scriptWhich shell to use with AWK?Dynamic VariablesThe Essential Syntax of AWKArithmetic ExpressionsUnary arithmetic operatorsThe Autoincrement and Autodecrement OperatorsAssignment OperatorsConditional expressionsRegular ExpressionsAnd/Or/NotSummary of AWK CommandsAWK Built-in VariablesFS - The Input Field Separator VariableOFS - The Output Field Separator VariableNF - The Number of Fields VariableNR - The Number of Records VariableRS - The Record Separator VariableORS - The Output Record Separator VariableFILENAME - The Current Filename VariableAssociative ArraysMulti-dimensional ArraysExample of using AWK's Associative ArraysOutput of the scriptPicture Perfect PRINTF OutputPRINTF - formatting outputEscape SequencesFormat SpecifiersWidth - specifying minimum field sizeLeft JustificationThe Field Precision ValueExplicit File outputFlow Control with next and exitAWK Numerical FunctionsTrigonometric FunctionsExponents, logs and square rootsTruncating IntegersRandom NumbersThe Lotto scriptString FunctionsThe Length functionThe Index FunctionThe Substr functionThe Split functionGAWK's Tolower and Toupper functionNAWK's string functionsThe Match functionThe System functionThe Getline functionThe systime functionThe Strftime functionUser Defined FunctionsAWK patternsFormatting AWK programsEnvironment VariablesARGC - Number or arguments (NAWK/GAWK)ARGV - Array of arguments (NAWK/GAWK)ARGIND - Argument Index (GAWK only)FNR (NAWK/GAWK)OFMT (NAWK/GAWK)RSTART, RLENGTH and match (NAWK/GAWK)SUBSEP - Multi-dimensional array separator (NAWK/GAWK)ENVIRON - environment variables (GAWK only)IGNORECASE (GAWK only)CONVFMT - conversion format (GAWK only)ERRNO - system errors (GAWK only)FIELDWIDTHS - fixed width fields (GAWK only)AWK, NAWK, GAWK, or PERL (adsbygoogle = window.adsbygoogle []).push();Intro to AWKCopyright 1994,1995 Bruce Barnett and General Electric CompanyCopyright 2001, 2004, 2013, 2014 Bruce BarnettAll rights reservedYou are allowed to print copies of this tutorial for your personaluse, and link to this page, but you are not allowed to make electroniccopies, or redistribute this tutorial in any form without permission. Original version written in 1994 and published in the Sun ObserverAwk is an extremely versatile programming language for working onfiles. We'll teach you just enough to understand the examples in thispage, plus a smidgen. The examples given below have the extensions of the executing script as part of the filename. Once you download it, and make it executable, you can rename it anything you want.Why learn AWK?In the past I havecovered grep andsed. This section discusses AWK, another cornerstoneof UNIX shell programming.There are three variations of AWK:AWK - the (very old) original from AT&TNAWK - A newer, improved version from AT&TGAWK - The Free Software foundation's versionOriginally, I didn't plan to discuss NAWK, but several UNIX vendorshave replaced AWK with NAWK, and there are several incompatibilitiesbetween the two. It would be cruel of me to not warn you about thedifferences. So I will highlight those when I come to them.It is important to know than all of AWK's features are in NAWK andGAWK.Most, if not all, of NAWK's features are in GAWK.NAWK ships as part of Solaris. GAWK does not. However, many sites onthe Internet have the sources freely available. If you user Linux, you have GAWK. But in general, assume that I am talking about the classic AWK unless otherwise noted.And now there is talk about MAWK, TAWK, and JAWK. Why is AWK so important? It is an excellent filter and report writer.Many UNIX utilities generates rows and columns of information.AWK is an excellent tool for processing these rows and columns,and is easier to use AWK than most conventional programming languages.It can be considered to be a pseudo-C interpretor,as it understands the same arithmatic operators as C.AWK also has string manipulation functions, so it can search forparticular strings and modify the output. AWK also has associative arrays,which are incredible useful, and is a feature most computing languageslack. Associative arrays can make a complex problem a trivial exercise.I'll try to cover the essential parts or AWK, and mention the extensions/variations.The "new AWK," or "nawk", comes on the Sun system, and you may find it superior to the old AWK in many ways. In particular,it has better diagnostics, and won't print out the infamous "bailing out near line ..." message the original AWK is prone to do.Instead, "nawk" prints out the line it didn't understand, and highlights the bad parts with arrows. GAWK does this as well, and this really helps a lot. If you find yourself needing a feature that is very difficult or impossible to do in AWK, I suggest you either use NAWK, or GAWK, or convert your AWK script into PERL using the"a2p" conversion program which comes with PERL. PERL is a marvelous language, and I use it all the time, butI do not plan to cover PERL in these tutorials.Having made my intention clear, I can continue with a clear conscience.Many UNIX utilities have strange names. AWK is one of those utilities.It is not an abbreviation for awkward. In fact, it is an elegantand simple language.The work"AWK" is derived from the initials of the language's three developers: A. Aho, B. W. Kernighan and P. Weinberger. Basic StructureThe essential organization of an AWK program follows the form:pattern action The pattern specifies when the action is performed.Like most UNIX utilities, AWK is line oriented. That is,the pattern specifies a test that is performed with each line readas input. If the condition is true, then the action is taken.The default pattern is something that matches every line.This is the blank or null pattern. Two other important patternsare specified by the keywords"BEGIN" and"END". As you might expect, these two words specify actions to be takenbefore any lines are read, and after the last line is read.The AWK program below:BEGIN print "START" print END print "STOP" adds one line before and one line after the input file.This isn't very useful, but with a simple change, we can makethis into a typical AWK program:BEGIN print "File\tOwner" print $8, "\t", $3END print " - DONE -" I'll improve the script in the next sections, but we'll call it "FileOwner".But let's not put it into a script or file yet. I will cover that part in a bit. Hang on and follow with me so you get the flavor of AWK.The characters"\t" Indicates a tab character so the output lines up on even boundries.The"$8" and"$3" have a meaning similar to a shell script. Instead of the eighth and thirdargument, they mean the eighth and third field of the input line.You can think of a field as a column, and the action you specifyoperates on each line or row read in.There are two differences between AWK and a shell processing thecharacters within double quotes. AWK understands special charactersfollow the"\" character like "t". The Bourne and C UNIX shells do not.Also, unlike the shell (and PERL) AWK does not evaluate variables within strings. To explain, the second line could not be written like this:print "$8\t$3" That example would print"$8 $3". Inside the quotes, the dollar sign is not a special character.Outside, it corresponds to a field.What do I mean by the third and eight field?Consider the Solaris"/usr/bin/ls -l" command, which has eight columns of information.The System V version (Similar to the Linux version), "/usr/5bin/ls -l" has 9 columns.The third column is the owner, and the eighth (or nineth) column in the name of the file.This AWK program can be used to process the output of the"ls -l" command, printing out the filename, then the owner, for each file.I'll show you how.Update: On a linux system, change "$8" to "$9".One more point about the use of a dollar sign.In scripting languages like Perl and the various shells, a dollar signmeans the word following is the name of the variable. Awk isdifferent. The dollar sign means that we are refering to a field orcolumn in the current line. When switching between Perl and AWK you must remener that "$" has a different meaning.So the following piece of code prints two "fields" to standard out. The first fieldprinted is the number "5", the second is the fifth field (or column) on the inputline.BEGIN x=5 print x, $xExecuting an AWK script So let's start writing our first AWK script.There are a couple of ways to do this.Assuming the first script is called "FileOwner", the invocation would bels -l FileOwnerThis might generate the following if there were onlytwo files in the current directory:FileOwnera.filebarnettanother.file barnett - DONE -There are two problems with this script.Both problems are easy to fix, but I'll holdoff on this until I cover the basics.The script itself can be written in many ways.I've show both the C shell (csh/tcsh), and Bourne/Bash/POSIX shell script.The C shell version would look like this:#!/bin/csh -f# Linux users have to change $8 to $9awk '\BEGIN print "File\tOwner" \ print $8, "\t", $3\END print " - DONE -" \'And of course, once you create this script, you need to make this script executable by typingchmod +x awk_example.1.cshClick here to get file: awk_example1.cshAs you can see in the above script, each line of the AWK script must have a backslash if it is not the last line of the script.This is necessary as the C shell doesn't, by default, allow strings to be longer than a line.I have a long list of complaints about using the C shell. SeeTop Ten reasons not to use the C shellThe Bourne shell (as does most shells) allows quoted stringsto span several lines:#!/bin/sh# Linux users have to change $8 to $9 awk 'BEGIN print "File\tOwner" print $8, "\t", $3END print " - DONE -" 'And again, once it is created, it has to be made executable:chmod +x awk_example1.shClick here to get file: awk_example1.shBy the way, I give example scripts in the tutorial, and use an extension on the filename to indicate the type of script.You can, of course, "install" the script in your home "bin" directory by typingcp awk_example1.sh $HOME/bin/awk_example1chmod +x $HOME/bin/awk_example1A third type of AWK script is a "native' AWK script, where you don't use the shell. You can write the commands in a file, and executeawk -f filenameSince AWK is also an interpretor, like the shell, you can save yourself a step and make the file executableby add one line in the beginning of the file:#!/bin/awk -fBEGIN print "File\tOwner" print $8, "\t", $3END print " - DONE -" Then execute "chmod +x" and ise this file as a new UNIX command.Click here to get file: awk_example1.awkNotice the "-f" option following '#!/bin/awk "above, which is also used in the third format where you use AWK to execute the file directly, i.e. "awk -f filename".The "-f" option specifies the AWK file containing the instructions.As you can see, AWK considers lines that start with a"#" to be a comment, just like the shell. To be precise, anything from the"#" to the end of the line is a comment (unless its inside an AWK string.However, I always comment my AWK scripts with the"#" at the start of the line, for reasons I'll discuss later.Which format should you use? I prefer the last format when possible.It's shorter and simpler. It's also easier to debug problems.If you need to use a shell, and want to avoid using too many files, you can combine them as we did in the first and second example.Which shell to use with AWK?The format of the original AWK is not free-form. You cannot put new line breaks just anywhere.They must go in particular locations.To be precise, in the original AWKyou can insert a new line characterafter the curly braces, and at the end of a command,but not elsewhere.If you wanted to break a long line into two lines at any other place, you had to use a backslash:#!/bin/awk -fBEGIN print "File\tOwner" print $8, "\t", \ $3 END print " - DONE -" Click here to get file: awk_example2.awkThe Bourne shell version would be#!/bin/shawk 'BEGIN print "File\tOwner" print $8, "\t", \$3END print "done" 'Click here to get file: awk_example2.shwhile the C shell would be#!/bin/csh -fawk 'BEGIN print "File\tOwner" \ print $8, "\t", \\$3\END print "done"\'Click here to get file: awk_example2.cshAs you can see, this demonstrates how awkward theC shell is when enclosing an AWK script.Not only are back slashes needed for every line, some lines need two, then the old original AWK is used.Newer AWK's are more flexible where newlines can be added.Many people, like me, will warn you about the C shell.Some of the problems are subtle, and you may never see them.Try to include an AWK or sed script within a C shell script, and the back slashes will drive you crazy.This is what convinced me to learn the Bourne shell years ago, when Iwas starting out (before the Korn shell or Bash shell were available). Even if you insist on use the C shell, you should at least learn enough of the Borne/POSIX shell to set variables,which by some strange coincidence is the subjectof the next section. Dynamic VariablesSince you can make a script an AWK executableby mentioning"#!/bin/awk -f" on the first line, including an AWK script inside a shell scriptisn't needed unless you want to either eliminate the need for an extra file, or if you want to pass a variable to the insides of an AWK script.Since this is a common problem, now is as good a time to explain thetechnique.I'll do this by showing a simple AWK programthat will only print one column. NOTE: there will be a bug in the first version.The number of the column will be specified by the first argument.The first version of the program, which we will call"Column", looks like this:#!/bin/sh#NOTE - this script does not work!column="$1"awk 'print $column'Click here to get file (but be aware that it doesn't work): Column1.shA suggested use is:ls -l Column 3This would print the third column from thels command, which would be the owner of the file.You can change this into a utility that counts how many files are owned by each user by addingls -l Column 3 uniq -c sort -nrOnly one problem: the script doesn't work.The value of the"column" variable is not seen by AWK. Change"awk" to"echo" to check. You need to turn off the quotingwhen the variable is seen. This can be done by ending the quoting, and restarting it after the variable:#!/bin/shcolumn="$1"awk 'print $'"$column"''Click here to get file: Column2.shThis is a very important concept, and throws experienced programmers acurve ball.In many computer languages, a string has a start quote, and end quote, and the contents in between.If you want to include a special character inside the quote, you must prevent thecharacter from having the typical meaning. In the C language, this is down by putting a backslash before the character.In other languages, there is a special combination of characters to to this.In the C and Bourne shell, the quote is just a switch.It turns the interpretation mode on or off.There is really no such concept as "start of string" and"end of string". The quotes toggle a switch inside the interpretor.The quote character is not passed on to the application.This is why there are two pairs of quotes above.Notice there are two dollar signs. The first one is quoted,and is seen by AWK. The second one is not quoted, so the shellevaluates the variable, and replaces"$column" by the value.If you don't understand, either change"awk" to"echo", or change the first line to read"#!/bin/sh -x". Some improvements are needed, however.The Bourne shell has a mechanism to provide a value for a variableif the value isn't set, or is set and the value is an empty string.This is done by using the format:$variable:-defaultvalueThis is shown below, where the default column will be one:#!/bin/shcolumn="$1:-1"awk 'print $'"$column"''Click here to get file: Column3.shWe can save a line by combining these two steps:#!/bin/shawk 'print $'"$1:-1"''Click here to get file: Column4.shIt is hard to read, but it is compact.There is one other method that can be used.If you execute an AWK command and include on the command line information in the following form:variable=valuethis variable will be set when the AWK script starts.An example of this use would be:#!/bin/shawk 'print $c' c="$1:-1"Click here to get file: Column5.shThis last variation does not have the problems with quoting the previous example had.You should master the earlier example, however, because you can use itwith any script or command. The second method is special to AWK.Modern AWK's have other options as well. See the comp.unix.shell FAQ.The Essential Syntax of AWKEarlier I discussed ways to start an AWK script. This section will discuss the various grammatical elements of AWK.Arithmetic ExpressionsThere are several arithmetic operators, similar to C. These are the binary operators, which operate on two variables:AWK Table 1Binary OperatorsOperatorTypeMeaning+ArithmeticAddition-ArithmeticSubtraction*ArithmeticMultiplication/ArithmeticDivision%ArithmeticModuloStringConcatenationUsing variables with the value of "7" and"3", AWK returns the following results for each operatorwhen using the print command:ExpressionResult7+3107-347*3217/32.333337%317 373There are a few points to make.The modulus operator finds the remainder after an integer divide. The print command output a floating point number on the divide, but an integerfor the rest. The string concatenate operator is confusing, since it isn't even visible. Place a space between two variables and the strings are concatenated together.This also shows that numbers are converted automatically into strings when needed.Unlike C, AWK doesn't have "types" of variables. There is one type only, and it can be a string ornumber. The conversion rules are simple. A number can easily beconverted into a string. When a string is converted into a number,AWK will do so. The string"123" will be converted into the number 123. However, the string"123X" will be converted into the number 0. (NAWK will behave differently,and converts the string into integer 123, which is found in thebeginning of the string).Unary arithmetic operatorsThe"+" and"-" operators can be used before variables and numbers.If X equals 4, then the statement:print -x;will print "-4". The Autoincrement and Autodecrement OperatorsAWK also supports the"++" and"--" operators of C. Both increment or decrement the variables by one. Theoperator can only be used with a single variable, and can be before orafter the variable. The prefix form modifies the value, and then usesthe result, while the postfix form gets the results of the variable,and afterwards modifies the variable. As an example, if X has thevalue of 3, then the AWK statementprint x++, " ", ++x;would print the numbers 3 and 5. These operators are also assignmentoperators, and can be used by themselves on a line:x++;--y;Assignment OperatorsVariables can be assigned new values with the assignment operators.You know about"++" and"--". The other assignment statement is simply:variable = arithmetic_expressionCertain operators have precedence over others;parenthesis can be used to control grouping.The statementx=1+2*3 4;is the same asx = (1 + (2 * 3)) "4";Both print out "74".Notice spaces can be added for readability.AWK, like C, has special assignment operators, which combinea calculation with an assignment. Instead of sayingx=x+2;you can more concisely say:x+=2;The complete list follows:AWK Table 2Assignment OperatorsOperatorMeaning+=Add result to variable-=Subtract result from variable*=Multiply variable by result/=Divide variable by result%=Apply modulo to variableConditional expressionsThe second type of expression in AWK is the conditional expression.This is used for certain tests, like the if orwhile. Boolean conditions evaluate to true or false. In AWK, there is adefinite difference between a boolean condition, and an arithmeticexpression. You cannot convert a boolean condition to an integer orstring. You can, however, use an arithmetic expression as aconditional expression. A value of 0 is false, while anything else istrue. Undefined variables has the value of 0.Unlike AWK, NAWK lets you use booleans as integers.Arithmetic values can also be converted into boolean conditions byusing relational operators:AWK Table 3Relational OperatorsOperatorMeaning==Is equal!=Is not equal to>Is greater than>=Is greater than or equal to 0 ) print "average is ", total/lines; else print "average is 0"; }Click here to get file: average.awkYou can pipe the output of "ls -s" into this filter to count the number of files, the total size, and theaverage size. There is a slight problem with this script, as itincludes the output of "ls" that reports the total. This causes the number of files to be off by one.Changinglines++;toif ($1 != "total" ) lines++;will fix this problem.Note the code which prevents a divide by zero.This is common in well-written scripts. I also initialize the variables to zero. This is not necessary, but itis a good habit.AWK Built-in VariablesI have mentionedtwo kinds of variables: positional and user defined.A user defined variable is one you create. A positional variable isnot a special variable, but a function triggered by the dollar sign.Thereforeprint $1;andX=1;print $X;do the same thing: print the first field on the line.There are two more points about positional variables that are very useful.The variable"$0" refers to the entire line that AWK reads in.That is, if you had eight fields in a line,print $0;is similar to print $1, $2, $3, $4, $5, $6, $7, $8This will change the spacing between the fields; otherwise, theybehave the same.You can modify positional variables.The following commands$2="";print;deletes the second field.If you had four fields, and wanted to print out the second and fourthfield, there are two ways. This is the first:#!/bin/awk -f$1="";$3="";print;and the second#!/bin/awk -fprint $2, $4;These perform similarly, but not identically.The number of spaces between the values vary.There are two reasons for this.The actual number of fields does not change.Setting a positional variable to an empty stringdoes not delete the variable. It's still there, but the contents has beendeleted. The other reason is the way AWK outputsthe entire line. There is a field separator that specifies what character to put between the fields on output.The first example outputs four fields, while the second outputs two.In-between each field is a space.This is easier to explain if the characters between fieldscould be modified to be made more visible. Well, it can. AWK provides special variables for just that purpose.FS - The Input Field Separator VariableAWK can be used to parse many system administration files.However, many of these files do not have whitespace as a separator.as an example, the password file uses colons.You can easily change the field separator character to be a colonusing the "-F" command line option. The following command will print out accounts that don't have passwords:awk -F: 'if ($2 == "") print $1 ": no password!"' "/tmp/file";You can append to an existing file, by using">>:" printf("string\n") >> "/tmp/file";Like the shell, the double angle bracketsindicates output is appended to the file, instead of written to an empty file.Appending to the file does not delete the old contents.However, there is a subtle difference between AWKand the shell.Consider the shell program:#!/bin/shwhile x=$(line)doecho got $x >>/tmp/aecho got $x >/tmp/bdoneThis will read standard input, and copy the standard input tofiles"/tmp/a" and "/tmp/b". File "/tmp/a" will grow larger, as information is always appended to the file.File "/tmp/b", however, will only contain one line.This happens because each time the shell see the">" or">>" characters, it opens the file for writing, choosingthe truncate/create or appending option at that time.Now consider the equivalent AWK program:#!/usr/bin/awk -f print $0 >>"/tmp/a" print $0 >"/tmp/b"This behaves differently. AWKchooses the create/append option the first time a file is opened forwriting.Afterwards, the use of ">" or">>" is ignored.Unlike the shell, AWK copies all of standard input to file"/tmp/b". Instead of a string, some versions of AWK allow you to specify an expression:# [note to self] check this one - it might not workprintf("string\n") > FILENAME ".out";The following uses a string concatenation expression to illustrate this:#!/usr/bin/awk -fEND for (i=0;i "/tmp/a" i; }Click here to get file: awk_example12.awkThis script never finishes, because AWK can have 10 additional files open, and NAWK can have 20.If you find this to be a problem, look into PERL.I hope this gives you the skill to make your AWK output picture perfect.Flow Control with next and exitYou can exit from an awk script using the exit command.#!/usr/bin/awk -f # lots of code here, where you may find an error if ( numberOfErrors > 0 ) exit If you want to exit with an error condition, so you can use the shell to distinquish between normal and error exits, you can include an option integer value.Let's say to expect all lines of a file to be 60 characters, and you want to use an awk program as a filter to exit if the number of characters is not 60.Some sample code could be#!/usr/bin/awk -f if ( length($0) > 60) exit 1 else if ( length($0) Numeric FunctionsNameFunctionVariantcoscosineGAWK,AWK,NAWKexpExponentGAWK,AWK,NAWKintIntegerGAWK,AWK,NAWKlogLogarithmGAWK,AWK,NAWKsinSineGAWK,AWK,NAWKsqrtSquare RootGAWK,AWK,NAWKatan2ArctangentGAWK,NAWKrandRandomGAWK,NAWKsrandSeed RandomGAWK,NAWKTrigonometric FunctionsOh joy. I bet millions, if not dozens, of my readers have been waitingfor me to discuss trigonometry.Personally, I don't use trigonometry much at work, except when I go off on a tangent.Sorry about that. I don't know what came over me. I don't usually resortto puns. I'll write a note to myself, and after I sine the note, I'll have my boss cosine it.Now stop that! I hate arguing with myself. I always lose.Thinking about math I learned in the year 2 B.C. (Before Computers)seems to cause flashbacks of high school, pimples, and (shudder)times best left forgotten. The stress of remembering those days musthave made me forget the standards I normally set for myself.Besides, no-one appreciates obtuse humor anyway, even if I find acute way to say it.I better change the subject fast. Combining humor and computers is a very serious matter. Here is a NAWK scriptthat calculates the trigonometric functions for all degrees between 0 and 360.It also shows why there is no tangent, secant or cosecant function.(They aren't necessary). If you read the script, you will learn of some subtle differences betweenAWK and NAWK.All this in a thin veneer of demonstrating why we learnedtrigonometry in the first place. What more can you ask for?Oh, in case you are wondering, I wrote this in the month of December.#!/usr/bin/nawk -f## A smattering of trigonometry...## This AWK script plots the values from 0 to 360# for the basic trigonometry functions# but first - a review:## (Note to the editor - the following diagram assumes# a fixed width font, like Courier. # otherwise, the diagram looks very stupid, instead of slightly stupid)## Assume the following right triangle## Angle Y## # # # a c# # # +------- Angle X# b## since the triangle is a right angle, then#X+Y=90## Basic Trigonometric Functions. If you know the length# of 2 sides, and the angles, you can find the length of the third side.# Also - if you know the length of the sides, you can calculate # the angles.## The formulas are##sine(X) = a/c#cosine(X) = b/c#tangent(X) = a/b## reciprocal functions#cotangent(X) = b/a#secant(X) = c/b#cosecant(X) = c/a## Example 1)# if an angle is 30, and the hypotenuse (c) is 10, then# a = sine(30) * 10 = 5#b = cosine(30) * 10 = 8.66## The second example will be more realistic:## Suppose you are looking for a Christmas tree, and# while talking to your family, you smack into a tree# because your head was turned, and your kids were arguing over who# was going to put the first ornament on the tree.## As you come to, you realize your feet are touching the trunk of the tree,# and your eyes are 6 feet from the bottom of your frostbitten toes.# While counting the stars that spin around your head, you also realize# the top of the tree is located at a 65 degree angle, relative to your eyes.# You suddenly realize the tree is 12.84 feet high! After all, # tangent(65 degrees) * 6 feet = 12.84 feet# All right, it isn't realistic. Not many people memorize the# tangent table, or can estimate angles that accurately. # I was telling the truth about the stars spinning around the head, however. #BEGIN # assign a value for pi.PI=3.14159;# select an "Ed Sullivan" number - really really bigBIG=999999;# pick two formats# Keep them close together, so when one column is made larger# the other column can be adjusted to be the same widthfmt1="%7s %8s %8s %8s %10s %10s %10s %10sn";# print out the title of each columnfmt2="%7d %8.2f %8.2f %8.2f %10.2f %10.2f %10.2f %10.2fn";# old AWK wants a backslash at the end of the next line# to continue the print statement# new AWK allows you to break the line into two, after a commaprintf(fmt1, "Degrees", "Radians", "Cosine", "Sine", "Tangent", "Cotangent", "Secant", "Cosecant");for (i=0;i 0) line = line $0; else printf("missing continuation on line %d\n", NR); print line;}Click here to get file: awk_example17.awkInstead of reading into the standard variables, you can specifythe variable to set:getline a_lineprint a_line;NAWK and GAWKallow thegetline function to be given an optional filename or string containinga filename. An example of a primitive file preprocessor, thatlooks for lines of the format#include filenameand substitutes that line for the contents of the file:#!/usr/bin/nawk -f# a primitive include preprocessor if (($1 == "#include") && (NF == 2)) # found the name of the file filename = $2; while (i = getline Click here to get file: include.nawkNAWK's getline can also read from a pipe.If you have a program that generates single line,you can use"command" getline;print $0;or"command" getline abc;print abc;If you have more than one line, you can loop through the results:while ("command" getline) cmd[i++] = $0;for (i in cmd) printf("%s=%s\n", i, cmd[i]);Only one pipe can be open at a time. If you want toopen another pipe, you must executeclose("command");This is necessary even if the end of file is reached.The systime functionThesystime() function returns the current time of day as the number of secondssince Midnight, January 1, 1970.It is useful for measuring how long portions of your GAWK codetakes to execute.#!/usr/local/bin/gawk -f# how long does it take to do a few loops?BEGIN { LOOPS=100;# do the test twice start=systime(); for (i=0;i 2ff7e9595c
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